Abstract: Patient data monitoring is a key issue for health and diseasemanagement. The use of wireless sensors within a body areanetwork (BAN) makes this task seamless and easy. A BANsystem is presented, which allows the connectivity of a widerange of heterogeneous body sensors to a portable hub devicethat is connectable to external networks (IEEE 802.11, GPRS). ThisBAN is based on the use of Zigbee/IEEE 802.15.4 standardtechnology and off-the-shelf modules. It is currently being used atthe European level for the detection and the prediction ofthe human physiological state in relation to wakefulness, fatigue, andstress applications in which users carrying out daily activities aremonitored in an unobtrusive and comfortable way. Characterised by itslow power consumption, low cost, and ability to connect awide range of heterogeneous sensors, this system can substantially improvethe performance of different services, especially those that are health related.